We are, once again, on the verge of genocidal counterinsurgency in Sudan. History must not be allowed to repeat itself.

By early 2004, it was clear that the ideologically Arabist and Islamist regime in Khartoum was waging a genocidal counterinsurgency war throughout the western region of Darfur. Yet months passed before a broad range of human rights, government and academic voices said as much, even as the consequences of silence and inaction were conspicuous. In February 2004 I argued on this page that a “credible peace forum must be rapidly created. Immediate plans for humanitarian intervention should begin. The alternative is to allow tens of thousands of civilians to die in the weeks and months ahead in what will be continuing genocidal destruction.”

This prediction was borne out in the months that followed, the most destructive phase of the Darfur genocide, in which African tribal groups were mercilessly targeted by soldiers and militias. Sadly, mortality from war-related causes continues to mount. But now we are debating how many hundreds, not tens, of thousands have perished from war-related causes in Darfur.

Today, another episode of genocidal counterinsurgency is beginning in another part of Sudan. Absent a vigorous international response, there will almost certainly be a reprise of ethnically targeted human destruction in the middle of the country, specifically within the Nuba Mountains region of South Kordofan, which has a rich mixture of African inhabitants.

Sudan was ravaged by a north-south civil war from 1983 to 2005; the war nominally ended with the Comprehensive Peace Agreement, signed by Khartoum and the southern Sudan People’s Liberation Movement. But key terms of the agreement were never fulfilled, among them “popular consultations” that were to give the people of South Kordofan a voice in how they were governed. The armed wing of the liberation movement was especially strong in the Nuba Mountains, and Khartoum saw a threat that it was determined to eliminate.

On June 5 a military campaign began in South Kordofan. It has rapidly escalated in ferocity, and disturbing accounts have emerged of the African people of the Nuba being rounded up in house searches and road checkpoints, and subjected to indiscriminate aerial bombardment. All signs point to a new genocide.

It will be similar to the 1990s, when Khartoum declared a jihad against the peoples of the Nuba (who practice a range of religions, including Islam). Because the Nuba Mountains are not geographically contiguous with South Sudan (with which the area is militarily, politically and culturally allied), its people were largely left to fend for themselves.

Then, the regime imposed a total blockade of humanitarian assistance from the south. Many starving Nuba were forced into “peace camps,” where receiving food was conditional upon conversion to Islam. Some who refused were tortured or mutilated. Khartoum’s decade-long campaign killed and displaced hundreds of thousands.

Today, reports from the ground and wire services detail heavy fighting underway in Kadugli, the capital of South Kordofan, and surrounding areas. There are multiple reports (including photos) of military aircraft such as MiG-29s attacking deep in the mountains; on Wednesday these attacks destroyed the key runway at Kauda, critical for transporting humanitarian supplies into the Nuba, a disturbing sign of how Khartoum will carry out the genocide.

Nearly all humanitarian operations in the region have ceased, as Khartoum denies the United Nations air clearances; workers for the U.N. Mission in Sudan have been evacuated or confined to their base. On June 8 that base was raided by Khartoum’s military intelligence, and the United Nations was effectively disabled.

Khartoum’s actions come just days after regime forces seized Abyei, whose indigenous residents are overwhelmingly Dinka Ngok and see themselves as part of the south. The 2005 peace agreement promised them a referendum for self-determination, which Khartoum has aborted. Last month the regime launched a military attack to seize Abyei; the U.N. High Commission for Refugees reports that some 113,000 civilians have fled south — virtually the entire Ngok population. They are living in extremely difficult conditions, and many will die. A U.N. report found that Khartoum’s actions were “tantamount to ethnic cleansing,” a decisive phrase that senior U.N. officials excised from later versions of the text.

The U.N. Security Council demanded on June 3 that Khartoum immediately withdraw its forces from Abyei, but the regime scoffed — as it has at previous council demands, including those bearing on Darfur. This is bad news for the people of Abyei and for the prospects of a just and peaceful separation of Sudan’s north and south, which is scheduled for July 9. For the Nuba people, such fecklessness spells catastrophe.

Too often with Sudan, empty demands and threats signal to the regime that the world is not serious about halting atrocities. Either the international community gets serious about preventing further violence in Abyei and the adjacent region of South Kordofan, or we will again see “tens of thousands of civilians . . . die in the weeks and months ahead in what will be continuing genocidal destruction.”

Eric Reeves, a professor at Smith College, is the author of “A Long Day’s Dying: Critical Moments in the Darfur Genocide.” He is a consultant to several human rights and humanitarian organizations in Sudan.

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Comments our editors find particularly useful or relevant are displayed in Top Comments, as are comments by users with these badges: . Replies to those posts appear here, as well as posts by staff writers.